Flyable model aircraft are generally driven by a propeller which in turn is driven by a small internal combustion engine. They are light weight structures largely made of low density materials such as balsa wood, so as to provide as large a lifting area relative to gross weight as possible. These craft characteristically have fixed wings, fixed vertical and horizontal stabilizers, a hinged rudder and hinged ailerons. The rudder and ailerons are hinged to fixed structure such as a wing or stabilizer, and are positioned by push pull actuators, which in turn are controlled by radio signals.
In order to connect the hinged rudder and ailerons to the actuator it is conventional practice to attach horns to them. The horn is rigidly attached to the rudder or aileron, and projects radially beyond the center of rotation of the hinge so as to act as a lever and exert a torque on the control surface to position it relative to the fixed surface. Horn structures for this purpose are well-known, and are used on every practical model, remotely controllable aircraft.
Full aircraft also utilize control horns, but their attachment to a hinged surface is generally a rather pedestrian sort of thing. The full aircraft has substantial areas and cross-sections of structural members to which the horn can readily be attached. Bolted, cemented and threaded attachments are common.
Structural standards of passenger carrying aircraft and of model aircraft are, of course, very different from one another. For one thing, the safety factors and redundant designs which must be incorporated in manned aircraft are pointless or at least redundant as to model craft. The encountered and applied forces in model aircraft would be considered negligible in any load carrying or passenger carrying aircraft.
For this reason and for other reasons, the criteria for a suitable control horn for model aircraft are unique to this field. A practical horn must be simple in construction, light in weight, easy to install correctly, and be reliably retained once it is installed. In addition, because this is primarily a hobby field, the device must be affordable.
Prior art horns for model aircraft do exist. They perform the same function after installation as the device of this invention performs after it is installed. However, they generally involve rather complicated means of attachment, or if they do not, then they provide less reliable or less convenient means. More complication leads to higher costs. Less reliability often leads to loss of the craft which is an even greater cost, and also a disappointment to a hobbyist whose pleasure is utlimately related to the length of time his craft survives, and to the performance of his aircraft.
It is an object of this invention to provide a control horn for a model aircraft which can readily and reliably be attached to a pivoted control surface which is structurally elegantly simple, and which can be produced for a very low cost.